A number of pharmacologically distinct ion channels have been identified in the nervous system. For example, several distinct subunits of the neuronal receptor type have been identified. Similar observations have been made with respect to gamma-amino butyric acid (GABA), glycine, and glutamate receptor families. The pair wise expression of cloned receptor subunits in Xenopus oocytes has shown that each subtype has different pharmacological and biophysical properties. Such results suggest the degree of complexity which exists in the number of receptors that can be formed from combinations of the various receptor subunits.
One means to gain a better understanding of the pharmacology of these many ion channel subtypes is to express individual subtypes (or various combinations thereof) in cultured cells. If there were a rapid, accurate means to identify cell lines which express functional ligand-gated ion-channels, a great deal could be learned about the pharmacology of these receptor subtypes. Such a rapid, accurate assay method would also enable one to screen compounds for agonist or antagonist properties with respect to known ligand-gated, cationic channels.